As an example of various interfaces for connecting a personal computer (hereinafter referred to as a “PC”) and peripherals together, there is known a wireless USB specification (Wireless USB Specification Rev. 1.0) according to which unwired USBs (Universal Serial Buses) are used.
Referring now to FIGS. 10 to 12, a description will be given of a system in which a plurality of PCs share one printer using wireless USBs mentioned above. FIG. 10 is a block diagram schematically showing an arrangement of a system in which a plurality of PCs share one printer using wireless USBs. FIG. 11 is a view schematically showing how commands and print data are sent and received between the PC and the printer connected together using the wireless USBs. FIG. 12 is a diagram schematically showing an arrangement of host information included in a beacon sent form the PC appearing in FIG. 10.
As a system in which a plurality of PCs share one printer using wireless USBs, a system that enables a plurality of PCs 10a to 10c to share one printer 30 as shown in FIG. 10 can be envisaged. The PCs 10a to 10c and the printer 30 have wireless USBs 11a to 11c and 31, respectively.
Here, the printer 30 cannot communicate with the plurality of PCs 10a to 10c via the wireless USBs 11a to 11c and 31 at the same time. This is determined by the wireless USB specification. Therefore, the printer 30 communicates with any one of the PCs 10a to 10c one-on-one.
For example, when print data created by an application of the PC 10a is to be printed by the PC 10a, a user gives a print instruction to a print driver installed in the PC 10a. In response to the print instruction, the printer driver sends a beacon for giving a print request to the printer 30 from the wireless USB 11a as shown in FIG. 11. The beacon is continuously transmitted for a predetermined time period (for example, five seconds). The beacon includes information such as a unique host ID assigned to the PC 10a and a unique device ID assigned to the printer 30 as shown in FIG. 12.
Upon receiving the beacon via the wireless USB 31, the printer 30 stars one-on-one connection processing for establishing a wireless communication with the PC 10a. First, the printer 30 obtains a device ID from the received beacon, and checks whether or not the device ID and a device ID held in the printer 30 correspond to each other. Here, when both of these device IDs do not correspond to each other, the printer 30 determines that the received beacon is not a beacon for the printer 30, and discards the received beacon.
When both of these device IDs correspond to each other, the printer 30 obtains a host ID from the received beacon, and checks whether or not the host ID corresponds to one of host IDs held in the printer 30. When both of these host IDs do not corresponds to each other, the printer 30 determines that the received beacon is not a beacon for the printer 30, and discards the received beacon.
The host IDs registered in the printer 30 are host IDs that are registered by initial connection processing (association) on the wireless USB 31 required at the time of installation of the printer 30. In this example, host IDs of the respective PCs 10a to 10c are registered in the printer 30. The initial connection processing is carried out so that the PCs 10a to 10c and the printer 30 can share CC (Connection Context: comprised of a host ID, a device ID, and a connection key), and has the following three phases, identification, authentication, and permission.
When it is determined in this way that the host ID and the device ID held in the printer 30 correspond to the host ID and the device ID, respectively, received from the PC 10a, the printer 30 sends a connection request to the PC 10a via the wireless USB 31.
The PC 10a having received the connection request from the printer 30 complies with the connection request, and sends spooled print data to the printer 30 via the wireless USB 11a. Upon completion of the transmission of the print data, the PC 10a sends a disconnection request so as to avoid occupation of the printer 30. The disconnection request can be sent from both the PC 10a and the printer 30.
In the above described way, a one-on-one wireless connection using wireless USBs is established between the printer 30 and the PC 10a, and a wireless communication is carried out between them. However, while wirelessly connecting to one PC, the printer 30 can receive beacons (print requests) from other PCs but cannot wirelessly connect to the other PCs. Thus, the printer 30 cannot sequentially accept print requests from the PCs 10a to 10c in order and process print data. That is, the printer 30 cannot print jobs from the PCs 10a to 10c in order.
To solve this, a system has been proposed which receives a beacon from a host, lists host information included in the beacon and holds the same, and sends a connection request to the host based on the listed host information (see PTL (Patent Literature) 1).
A description will be given of the proposed system with reference to FIGS. 10, 13, and 14. FIG. 13 is a diagram showing a host list held by the printer. FIG. 14 is a diagram showing the sequence of processing carried out by the printer in accordance with the host list.
For example, the PC 10a sends a beacon 1000a (print request) via the wireless USB 11a as shown in FIG. 10. Subsequently, the same PC 10a sends a beacon 1001a (print request) via the wireless USB 11a. Further subsequently, the PC 10b sends a beacon 1000b (print request), and the PC 10c sends a beacon 1000c (print request).
In this case, the printer 30 sequentially receives the beacons 1000a, 1001a from the PC 10a, the beacon 1000b from the PC 10b, and the beacon 1000c from the PC 10c. 
As shown in FIG. 13, the printer 30 registers on a host list 40 host IDs included in the beacons 1000a, 1001a, 1000b, and 1000c, respectively, in the order in which they were received. The host list 40 is comprised of a write column 42 to which registration numbers 41 are assigned. The registration numbers 41 are indicative of the order in which beacons are received by the printer 30, and the order in which connection requests are given to the PCs 10a to 10c. Also, host IDs as transmission sources of received beacons are written in the write column 42.
As shown in FIG. 14, the printer 30 refers to the host list 40, and first, sends a connection request to the PC 10a registered as the registration No. 1 on the host list 40 (500). Then, when a wireless connection with the PC 10a is established, the printer 30 receives print data sent from the PC 10a (501), and upon completion of the reception of the print data, the printer 30 sends a disconnection request to the PC 10a (502).
Then, the printer 30 sends a connection request to, receives print data from, and sends a disconnection request to the PC 10a registered as the registration No. 2 on the host list 40 (503 to 505). After that, a connection request is sent to, print data is received from, and a disconnection request is sent to the PC 10b in order (506 to 508), and a connection request is sent to, print data is received from, and a disconnection request is sent to the PC 10c in order (509 to 511).
As described above, the printer 30 registers on the host list 40 host IDs of the PCs 10a to 10c in the order in which beacons (print requests) were received from the plurality of PCs 10a to 10c, so that print jobs requested by the PCs 10a to 10c are processed in the order in which the print jobs were requested.
Moreover, as an example of systems in which a plurality of PCs share one printer, there is a system in which a plurality of PCs and one printer are connected together via a network such as a LAN. For this system, there has been proposed a technique for the printer to list and manage print requests from the plurality of PCs, and process print data requested to be printed by the PCs in the order in which print requests were given (see PTL 2).